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Whether it’s a large international airport or a reliever airport, they require TLC. Superior performance is not just a requirement but a necessity when you’re talking about a variety of high-speed aircraft flying in and out of an airport, and potentially millions of passengers using airport facilities. From the hangar to the terminal to the taxiway to the runway – airports must invest in maintenance and expansion to continue to service current carriers and expand their offerings. With the constant wear from heavy aircrafts, fuel emissions, and the elements, etc., it’s not hard to imagine that airport concrete and pavement need to be cared for. As for airport facilities, there are terminals, parking lots, parking ramps, bridges, and tunnels, which need to successfully serve passengers every day, around the clock, every time. Meeting airport user and facility needs is easier said than done, and it takes a multidisciplinary approach to make it happen.

Book your funding

For many airports, large rehabilitation or expansion projects can take many years of planning before construction to attain the necessary funding to support the project. Despite the variety of grant programs available to airports, one principle remains true for most – funds are not given unless you can prove the need for improvement. Data is key when trying to display the urgency for project funding. Gathering test data early in the planning process can provide the support needed to secure funding. For instance, taking a data-rich approach to testing could include: performing falling weight deflectometer (FWD) testing for analyzing pavement structure, utilizing ground penetrating radar (GPR) to evaluate existing layer thickness, testing pavement cores, analyzing soil borings, evaluating environmental concerns such as deicing chemicals, determining the susceptibility of

existing structures to vibrations, and learning where existing utilities and footings are located.

Many of the funding sources, state and federal, share a portion of the improvement costs with the airport owner. Oftentimes, this spreads projects out over a couple of years to allow the airport time to gather its portion of the funding. In some cases, like at Minneapolis-St. Paul International Airport (MSP), development fees are based on ticket surcharges and contracts with facility users. The dependency on market conditions causes fluctuations to both airport revenues and facility user demand and needs.

Ready for Takeoff Getting airport projects off the ground presents distinct challenges

See Ready for Takeoff - Continued on page 4

By Matthew Ruble, PE, Aaron Tast, Tim Lenway, MPH, and Jena Barch

Falling weight deflectometer (FWD) testing is used to evaluate the pavement structure condition. Based on the FWD test data, recommendations can be made for design work.

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Practical and Entertaining Since 19972

The constructed world is dominated by the use of rock and sand to provide sustainable infrastructure throughout the globe. Rock and sand in technical

parlance are frequently referred to as aggregates in the construction industry, and typically are separated into three major classifications: coarse, intermediate and fine. The typical concrete mix design may contain up to 80 percent aggregates by volume. Not only does the road you drive on everyday contain aggregates, but more than likely that road rests on a bed of aggregates. Aggregates are an important part of the long-term viability of our society. But, will any aggregates do? Can we just wash and size aggregates to our needs?

Going the distance

The Northern states of the U.S. have been blessed with fairly durable aggregates ready for the taking. Chances are that if you live in the Northern states, there probably is a sand and gravel deposit near you supplying aggregates for roads, bridges, airports, homes and schools. Although we are very fortunate to have quality aggregates that are locally available, other geographic locations aren’t so lucky. For instance, say you’re tasked with building a military facility on a

tropical island in the middle of the Pacific Ocean – you’re probably not able to readily quarry aggregates on location.

In a recent instance, this exact situation arose. The structure being built had to serve both a practical and tactical purpose, with the latter presenting a greater challenge. Reason being, there is no room for even a minor defect in the case of national defense. The structure must perform and be sustainable. In order for the structure to accomplish both roles, the concrete’s aggregate mixture needed to contain a specific form of igneous rock called basalt to resist direct blasts from jet engines. The island had both ancient limestone reef deposits and igneous rocks, but both were deemed inadequate for construction due to their material properties. To meet the requirements, materials were quarried and shipped to the island from a quarry more than 1,600 miles away.

In another instance, an international airport on a tropical island was in need of repair for an aging infrastructure. Local sources for coarse aggregate were not available; no sufficient mining operations existed on the tiny island, and the local rocks were not appropriate for use. The airport fell under the U.S. Federal Aviation Administration’s (FAA) general specifications for construction requiring several performance properties to be attained, including freeze-thaw durable aggregates. Even though the tiny island was a few hundred miles north of the Equator, the freeze-thaw durability requirement was not waived. In order to meet the intent of the specification, an aggregate located 2,900 miles away that met the requirements was quarried and shipped by barge to the construction site on the island. Not only did the construction team need to address the material performance requirements, they also had to deal with the consequence of transporting the aggregate to the island. Given the long haul by barge, the team had to address the increased natural chloride ion content that would result from seawater saturating the aggregate during its voyage. If left unchecked, this chloride ion level increase in the coarse aggregate could lead to potential corrosion of the embedded steel within the concrete structures. That’s how far another site went to build a compliant and resilient structure.

In situations like these, economic forces typically dictate. If it needs to get done, there are solutions, but they tend to be expensive and must be evaluated for their overall benefits.

Moving Mountains, One Rock at a TimeTaking quality aggregates to new heights

By Jamison Langdon, jlangdon@braunintertec.com

Aggregates of varying rock types are used to meet general construction requirements. The aggregates represented above include glacial, river, and quarried igneous and carbonate rocks.

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Extreme Testing for Aggregate QualityThe need for aggregate testing is often based upon a material performance specification written into a contract, either commercial or governmental. When this occurs, chances are that extensive testing of aggregate performance is going to be required. This can range from the simple, “is the aggregate pure quartz?” to the complex, “what is the mineralogy of the aggregates and their distribution within the sample?” To address the gamut of questions, there are several categorical classes that speak to the quality of the aggregate, including mineralogy, petrology and physical properties.

For example, when representatives from the Andersen Air Force Base in Guam needed to determine if crushed limestone available on the island was suitable for use in a new concrete runway, it shipped samples to Braun Intertec for a preconstruction evaluation. To evaluate the limestone, we tested the aggregate samples per the normal evaluations within ASTM C 33, “Standard Specification for Concrete Aggregates,” along with an additional two protocols: ASTM C 295, “Standard Guide for Petrographic Examination of Aggregates for Concrete” and the U.S. Army Corps of Engineers protocol CRD-C 130-01, “Standard Recommended Practice for Estimating Scratch Hardness of Coarse Aggregate Particles.”

To meet the procedural requirements, an experienced petrographer had to identify every aggregate particle in two, 200-pound samples. The particles were hand sorted into similar aggregate types. For this project, the classification process went into greater detail than just describing a rock as a “limestone.” Classification could be based on a combination of characteristics such as sparry calcite, micritic limestone, biolithite, or some other carbonate rock term, including whether or not the particle is hard or soft, vuggy, or dense, etc. – each one of these descriptors conveying details about the aggregate. To put this step into perspective, more than 1,000 individual rocks were observed per sample. The classification process was performed on two samples for each evaluation, including the initial evaluation as well as three additional quality control checks during the runway construction. In all, nearly 10,000 particles were classified by the time the runway was built.

Trays of aggregate samples await classification and potential evaluation for scratch hardness. For each sample, more than 1,000 individual rocks were observed by hand.

Use it wisely

Granted, we are not looking to ship aggregates in from distances as far off as Alaska anytime soon. But, the reality is that some of the best reserves of aggregates are being built on or paved over. Already, aggregates are being transported an excess of 60 miles or more to the Minneapolis and St. Paul market to meet demand. Moving forward as a society, we need to make sure we are using raw materials wisely. This becomes more than simply a reduce, reuse and recycle argument for aggregates. We need to rethink the systems that carry our traffic, divert our surface runoff, and build our communities, in order to continue providing exceptional infrastructure for a thriving economy.

As can be seen, sometimes you don’t have to go very far for quality materials. And sometimes, you have to move a mountain (of aggregate) across an ocean.

Moving Mountains - Continued from page 2

Practical and Entertaining Since 19974

Depending on the limitations set forth by the funding source, they often dictate what can and cannot be worked on. For example, if an airport received funding to resurface or replace a runway, and during construction contaminated soils are encountered, the airport may not be able to use the funding to develop a Remedial Action Plan (RAP). Surprises like these can drastically delay projects and incur unexpected project costs on the owner. Many times, these surprises can be avoided by doing more site investigation in the planning stage.

Final approach into design

Not only does a site evaluation pay off from a funding perspective, but it helps inform the design recommendations available. For instance, pavement management data collected from runways, taxiways, and aprons can help determine if the pavement needs to be removed completely or if a more modest repair method, such as microsurfacing (see page 7, “Going Thin to Keep Pavements Healthy”), is a viable option for airport facilities. Also, understanding the impact of soil composition, variability, and moisture content is crucial to refining such designs and maintenance plans, making accurate estimates of construction costs for grant applications, and eliminating cost overruns – critical factors given the tight turnarounds for many airport projects.

On fully developed facilities, ease and speed of construction may be more important considerations in the design process than cost. In some cases, there may not be room to construct a typical spread footing foundation system with an open-cut earthwork system. Shoring and/or a foundation system of micropiles or helical anchors

may be needed to reduce construction time and interference with facility users. Oftentimes, the construction plans must allow for work to be performed in short windows of time each day.

Moreover, other important concerns such as ease of maintenance and life expectancy of materials combined with the need for the structures to support potentially millions of travelers each year, likely outweigh the need for the cheapest products. Not to mention, the runways and tarmacs must be able to sustain tremendous vehicle loads (weight and volume), as well as abuse from chemicals associated with the maintenance and operation of aircrafts. Extensive planning and data-rich evaluations provide the necessary information for designing and constructing a better project. They also may limit having to reconstruct or perform extensive maintenance in the future.

Cleared for construction

After years of planning, it’s a rush to get the project done. Often dependant on when funding comes through, timing doesn’t necessarily allow for a full construction season. And, let’s not ignore the massive production it takes to shut down part or all of an airport. With all these factors, not only does construction need to move fast, but testing needs to be done quickly and accurately.

Material durability is addressed during design but is ultimately determined by the quality of materials and processes during construction. It’s very important to have top-quality materials to minimize maintenance costs and extend the life expectancy of materials. To accomplish this, it requires thorough evaluation and inspection of materials during batching, fabrication and installation.

Ready for Takeoff - Continued from page 1

Nobody likes the headache or cost associated with unforeseen contamination. That’s why performing environmental sampling for common airport chemicals, such as jet fuel and glycol-based deicing agents, in the early phase of a project is essential for contaminant evaluation and mitigation planning. Oftentimes, environmental sampling can be conducted in conjunction with geotechnical drilling, and the environmental information can be incorporated into a project-specific testing and disposal plan. The plan establishes roles and responsibilities for site remediation, and can be incorporated into the project specifications.

The Federal Aviation Administration (FAA) requires airports to obtain stormwater discharge permits under the National Pollutant Discharge Elimination System (NPDES) program, and make sure that wastes from deicing operations are properly collected and treated. The Environmental Protection Act (EPA) also requires certain facilities to implement a Spill Prevention Control and Countermeasure (SPCC) Plan to reduce or eliminate aqueous chemical discharges. Changes to airport operations or construction of new facilities can trigger NPDES and/or SPCC modifications and associated reporting. Potential permit modifications should be evaluated during the preplanning and site selection process.

T u r b u l e n c e !

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Examples include evaluating aggregate properties prior to concrete batching, X-rays of weld quality on pipe materials, and coating inspections of tanks and other products. Moreover, evaluating the building envelope through peer review of architectural details, and testing and inspection of the envelope during construction will help avoid costly damage and delays.

Producing quick, quality test results requires a solid understanding of the Federal Aviation Administration (FAA) and state specifications. For example, the FAA is concerned with using aggregates that are freeze-thaw durable and not alkali-silica reactive. Prior to construction, Braun Intertec partners with suppliers and contractors to evaluate the freeze-thaw durability of concrete to specifications required by the FAA, and during construction, we monitor the aggregate through multiple quality checks. For more information on the quality process for aggregates, see page 2, “Moving Mountains, One Rock at a Time.” Overall, many of the specifications require more testing procedures

than typical road construction projects, as well as real-time data to watch for failures so adjustments can be made promptly. It’s important to understand the ins and outs of these specifications and stay abreast of modifications to streamline processes and enforce quality standards.

A recent, distinct example of a project that needed to be done right the first time with no room for error was the mill and overlay of runway 13-31 at the Detroit Lakes-Becker County Airport in Detroit Lakes, Minn. The project needed to be completed in five days, which included milling of the runway and overlaying with 1 1/2 inches of FAA P-401 surface course. After milling was complete, Braun Intertec and the contractor performed and analyzed a bituminous test strip. It required three samples of the bituminous mixture properties and six core density samples to determine compliance with FAA specifications before overlay could proceed. The specifications were met the first time, and the contractor completed paving within three days – without any pavement deductions. During paving, Braun Intertec performed quality assurance testing, including 10 samples of the bituminous mixture properties at an accelerated rate of one test per 500 tons of bituminous in two days. We also performed density testing on 20 core samples of the bituminous mat and longitudinal joints; all samples met specifications. Because of the tightly managed timeline and constant monitoring of materials and process, the airport opened the runway on time. It takes constant collaboration and communication with all stakeholders to keep airport projects moving quickly without sacrificing quality.

Even the best designed project can be a disaster with poor construction. Implementation of an appropriately prepared and executed quality control and quality assurance program will provide guidance on whether construction is meeting the design intent. Next time you race through the terminal or watch the runway flash by, know that it took an army of experts to see to the quality and care of each project.

Ready for Takeoff - Continued from page 4

Implementation of an appropriately prepared and executed quality control and quality assurance program will provide guidance on whether construction is meeting the design intent.

It takes constant collaboration and communication with all stakeholders to keep airport projects moving quickly without sacrificing quality.

Practical and Entertaining Since 19976

Dear Professor: When you design an embankment, what is the standard over-build to account for settlement? I have been reading some articles addressing settlement in roads built over deep excavations that are making my eyes hurt. Let’s say were talking about an embankment built to typical construction specifications – moisture content at ± 2 percent of optimum and compaction to at least 95 percent of standard Proctor dry density. —That Two-Tenth Grade Shortage Can’t Be On Me!

Great question (and I have one for you when we’re done here)! First, let me put down the controls to my RC dozer so I can give you my full attention. Embankment settlement occurs from two sources: (1) compression of the foundation soils under the weight of the fill, and (2) compression of the fill under its own weight. The magnitude of settlement that occurs from compression of the foundation soils is a function of the soils’ thickness, degree of compressibility, hydraulic conductivity, the rate of fill placement, and the time at which you are interested in measuring settlement. The magnitude of settlement that occurs from compression of the fill under its own weight is a function of the fill’s composition, thickness, and, as you indicated, moisture content and compaction. That’s a lot of stuff to keep track of …

Unfortunately, there aren’t any rules of thumb that will give you an answer you can use on all your future jobs. All you can really do is rely on the design team to address the settlement issue during the exploration and analysis stage of the project, and in the preparation of project plans and specifications. A lot of geotechnical resources will help tell you where you’re headed from a relative magnitude standpoint, but none will do so to the tenth of a foot. From a worst case perspective, the Muskeg Engineering Handbook claims that organic soils can compress up to one-third their original thickness, which makes your two-tenths grade shortage seem pretty small. Rock is pretty much incompressible, and the rest of the world’s soils fall somewhere in between. For the 20-foot high embankments, we monitored along your recent North Dakota highway project,

settlement did not exceed 1 1/2 feet, and that was where the fill was placed on 10 to 15 feet of soft clay. Again, however, compression of the foundation soils is only one part of the puzzle. With regard to self-weight compression of fill, monitoring we’ve performed suggests that fill can compress two-tenths to three-tenths of a percent of the fill height per log cycle of time, or 0.02H/cycle to 0.03H/cycle (cycles being 1 day, 10 days, 100 days, 1,000 days, etc.). The Naval Facilities Engineering Command (NAVFAC) Design Manual 7.02, “Foundations and Earth Structures,” suggests similar magnitudes of self-weight compression of fill. As such, 20 feet of fill could compress 1/2 to 3/4 inch per log cycle of time (more than two-tenths!). Given the length of the initial “cycles,” you wouldn’t likely measure an appreciable amount of settlement until you were on track to measure the 100-day, 1,000-day, and later increments, but you still could see 1 to 2 inches of post-placement settlement of that 20-foot fill.

Now back to my promise of a question for you: How is it that this shortage is on your dime? I’m assuming that your work complied with the project plans and specifications relative to the selection, placement and compaction (including moisture content) of the fill, as well as the verification of design grades. I hope that the plans and specifications, and the project’s geotechnical report both addressed anticipated embankment settlement (due to compression both of the foundation soils and the fill) and the measures needed (over-building, surcharging, etc.) to mitigate it. If not, I am a bit disappointed! —The Professor

Ask The Professor By Charles Hubbard, PE, PGchubbard@braunintertec.com

©2012 Braun Intertec Corporation

Mr. Heavy Equipment Oper-aaaa-tor (remember those “Real Men of Genius” commercials?):

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Everybody loves a smooth landing. The Federal Aviation Administration (FAA), who through the National Plan of Integrated Airport Systems

(NPIAS) provides funding to more than 3,400 of the nation’s airports, has committed to them with a stated goal to maintain at least 93 percent of runway pavements in “fair” condition or better. This would typically mean scoring at least 40 out of 100 on the 0-100 Pavement Condition Index (PCI) rating system, with 100 representing a pavement in perfect condition. A pavement with a PCI score of 40 is just good enough to fix with a cheaper option, such as asphalt overlay. Below this threshold, much costlier pavement reconstruction becomes necessary.

Using actual field surveys in 2009, the FAA reported that 97 percent of runways were in fair or better condition, so clearly their goals are serious. In fact, these so-called “goals” are essentially explicitly legislated with significant federal funds hanging in the balance. Any grant issued to an airport with a federal component involving the rehabilitation or reconstruction of airport pavements is required to contain assurance that a proper pavement management system, as defined by the FAA, is in place and being utilized correctly.

In other words, the federal government, who could be providing up to 95 percent of project funds under the Airport Improvement Program (AIP), wants the best long-term returns possible on its material investments. The recent, steady rise in material costs makes front-loading these projects a wise defense against future inflation, but the effort is moot if the new pavements are not properly maintained.

Ideally, pavement conditions would be kept above “fair” indefinitely through relatively cheap preventive maintenance alone. Crack seal, already used routinely by a vast majority of airports with asphalt pavements, will only stave off ruin for so long. Since some loss in condition with time is inevitable, what to do? Microsurfacing, a cold-placed surface treatment, provides a versatile, moderate solution where crack seal will no longer cut it and an asphalt overlay seems like overkill.

Microsurfacing consists of high-quality crushed aggregate, polymer-modified emulsion, mineral filler, water and other additives.

The thickness of most microsurfacing layers is typically less than half an inch, so grades can generally be preserved. The asphaltic slurry is applied cold, with no compaction necessary, and breaks chemically (via various engineered additives) rather than thermally. This means it can be placed and opened to unrestricted traffic after only 45 minutes to two hours – a huge advantage for maintaining traffic at busy airports.

Just like a slurry seal or chip seal you might see on a residential street, microsurfacing can be applied to seal minor cracks, restore surface friction and reduce oxidation of the asphalt surface. Unlike a chip seal, microsurfacing’s crushed aggregate forms a tight aggregate matrix, which functions in itself as a durable wearing surface that can

resist the abrasion of landing and takeoff on airport runways on both asphalt and concrete pavements. It also can be used to fill significant ruts (up

to 3/4 inch or more), a benefit it shares with its costlier cousin the asphalt overlay. Although it won’t provide the same pavement life as an overlay, anywhere from five to eight years of service should be expected at a price 50 percent less than a typical overlay treatment.

Despite that very few airports currently use microsurfacing, there is definitely a case to be made for going thin to keep pavements healthy. The fate of potential funding could hang in the balance.

Going Thin to Keep Pavements HealthyMicrosurfacing for airport facilities

Runways with moderate-severity cracking and no structural defects can benefit from a microsurfacing application rather than a costlier asphalt overlay.

By Neil Lund, PE, nlund@braunintertec.com

Microsurfacing, a cold-placed surface treatment, provides a versatile, moderate

solution where crack seal will no longer cut it and an asphalt overlay seems like overkill.

11001 Hampshire Ave. SMinneapolis, MN 55438

braunintertec.com

Minneapolis 800.279.6100Bismarck 701.255.7180Cedar Rapids 319.365.0961 Dickinson 701.255.7180Duluth 218.624.4967Fargo 800.756.5955Hibbing 800.828.7313La Crosse 800.856.2098Little Falls (Geothermal) 320.632.1081Mankato 800.539.0472 Milwaukee 262.513.2995 Minot 701.420.2738Rochester 800.279.1576Saint Cloud 800.828.7344Saint Paul 800.779.1196

Questions, requests and comments

Charles Hubbard, PE, PGBraun Intertec Corporation1826 Buerkle RoadSaint Paul, MN 55110Phone: 651.487.7060chubbard@braunintertec.com

©2012 Braun Intertec Corporation

This newsletter contains only general information. For specific applications, please consult your engineering or environmental consultants and legal counsel.

Geothermal System Lands at Duluth International Airport Duluth International Airport is one of the first airports in Minnesota to receive a Federal Aviation Administration (FAA) Voluntary Airport Low Emissions Program (VALE) grant. The VALE program is designed to reduce sources of ground emissions associated with the operation and maintenance of airport facilities, and help airports meet their state-related air quality responsibilities. The receipt of the $3.8 million grant is allowing the airport to design and construct a geothermal heating and cooling system for a new 110,000-square-foot passenger terminal. Braun Intertec Geothermal is consulting on the project, and working with Kraus Anderson and the Duluth Airport Authority (DAA) to obtain the most cost-efficient heating and cooling system possible within the challenging airport environment and geologic conditions typical of the Duluth area.

The geothermal system, which consists of 80 vertical heat exchangers drilled to a depth of 500 feet in very challenging gabbro, is estimated to save more than $30,000 in terminal utility costs annually as compared to a traditional heating and cooling system. The new terminal is expected to be completed early in 2013.

For more information about this project and Braun Intertec Geothermal services please visit our website at http://www.braunintertec.com/Services/GeothermalConsulting.aspx

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